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The extraction and separation mechanisms are the following:
Extraction:
3+ −
M + 3NO + 2 DIAM ⇔M(NO ) (DIAM)
(3)
3 3 3 2
An(III)/Ln(III) separation: done after contacting the loaded solvent with a pH adjusted aqueous
solution containing DTPA selective trivalent actinide complexing agent. For pH range HDEHP
is the extractant, while at the metal nitrate extraction step, carried out with acidic feeds 3 to
5 mol/L in nitric acid, trivalent An and Ln are extracted with the malonamide.
This process was recently successfully tested in the ATALANTE facility (CEA/Marcoule, France).
The possible drawbacks of this process are the: (i) necessity to use 2 extractants, (ii) need of pH
adjustment, (iii) co-extraction of numerous ions, (iv) solvent clean-up not yet defined.
Multi-cycle processes
• 1 st step: An+Ln co-extraction
TRUEX (USA, Japan, Russian Federation, Italy and India)
This process is based on the use of the CMPO extractant. This process was developed by
Horwitz (ANL) and Schulz (Hanford) in the USA in the 80s. The advantages of the TRUEX
process are the following: (i) it can extract An (and Ln) salts from acidic feeds, (ii) its efficiency
has been demonstrated with genuine HAWs, (iii) a large experience has been gained worldwide.
The main drawbacks of the TRUEX process are the: (i) necessity to use large concentration of
tri-n-butylphosphate (TBP) as solvent modifier added to the solvent to prevent third phase
formation, (ii) stripping of metal ions which are not so efficient, (iii) delicate solvent clean-up.
DIAMEX (France, Italy, Germany, Europe, Japan, USA and India)
This process is based on the use of a malonamide extractant. The main interests of the process
are: (i) An (and Ln) salts can be extracted from acidic feeds, (ii) its efficiency has been
demonstrated on genuine HAWs, (France, Europe), (iii) no secondary solid wastes generated
owing to the CHON character of the malonamide extractant. Its main drawback relies in the
partial co-extraction of palladium (Pd) and ruthenium (Ru) with the MAs.
A process based on a new type of diamide, a diglycolamide (DGA), which is a terdendate
ligand having better affinity for An(III) than the malonamide, is under development at JAERI
(Tokai, Japan).
TRPO (INET, Tsinghua University, China)
The TRPO process is based on the use of a mixture of tri-alkyl phosphine oxides (R3P(O), with
R = alkyl groups) as extractant. This process has been tested successfully in China with genuine
HAW. Its main drawbacks concern the necessity: (i) to adjust the feed acidity, (ii) to use a
concentrated nitric acid solution for An(III)+Ln(III) stripping, which complicates the
subsequent An(III)/Ln(III) partitioning step.
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